Hi Robert, I can't speak for Eric but I can say something about design guidelines in datasheets and app notes. The board layout guidelines you might see in datasheets are normally mirrored from specific test boards or evaluation products. So the manufacturer is really only telling you that the circuit/component worked in their specific situation, they can't guarantee the component will work in every situation. This is why you keep getting the ferrite bead on power lead guidelines all over the place. It works in certain situations but it makes high frequency noise worse in other situations, and yet the guideline was probably developed for a totally different situation. So in that sense, the guidelines aren't universally wrong if your only metric for success is to ensure you get a working circuit, but that doesn't mean the circuit will be low noise or pass EMC.

Thank you! Cheers!

This stuff with grounding and parasitics is a lot more important in instances where: 1) you're operating with typical digital ICs, and 2) you're working with very low signal levels, like micro-volts. In the first case you're at higher frequencies, but you get the most benefit and ease of routing when you put the GND plane below the signal layer, and ideally as close to the signal layer as possible. In the latter case you could be working at any frequency, so it would also apply in analog measurements at audio frequencies. In that case where you are taking low-level analog measurements, you would also use a lot of filtering, isolation with splitting up planes and adding a lot of stitching around signal paths. Also you're right, an intentionally placed cap or RC circuit will beat parasitic capacitive impedance hands down, that's one reason we might place a cap across PGND and SGND on a transformer. The intentionally placed capacitor will be the signal path rather than the winding capacitance across the TX as long as the placed cap is larger capacitance than the parasitic.

I just sent an email over to Eric to verify that this is correct, I'll follow up ASAP

@@Zachariah-Peterson Thanks Zach, appreciate your response!

Hi Pravin, that's a great idea for a video, I'll put it on my list to create over the holiday break!

@@Zachariah-Peterson Thanks a lot.Its helpful for us.🙏😊